We are all familiar with the basics of viruses: These particles infect living cells and wreak havoc throughout the body. But viruses aren’t the only villains around causing chaos in living things. Other infectious agents called viroids and prions — which are also tiny but powerful — can take down both plant life and entire animals.

Viroids are free RNA molecules of low molecular weight without any protein coat, while viruses can have either RNA or DNA molecules encapsulated in a protein coat. Viroids are smaller in size than viruses.

Viroids not made of cells.

Viroids don’t transform energy.

Viroids can’t reproduce on their own.